Midterm Flashcards
Dose of fentanyl
5-10 mcg/kg (50-100 mcg clinical)
Dose of propofol
1-2 mg/kg
Dose of etomidate
0.2-0.3 mg/kg
Dose of Versed
0.1-0.2 mg/kg (1-2 mg clinical)
ketamine dose
2-4 mg/kg (10-50 mg clinical)
What stage of awareness is a MAC case?
3- subconscious, implicit recall
What stage of awareness is a general anesthesia case?
4- no awareness or recall
MoA of inhalational agents
activate GABA and glycine, inhibit glutamate
What is MAC?
minimum alveolar concentration- concentration required to keep 50% of humans from moving in response to painful stim
VP of halothane
244
VP of isoflurane
240
VP of desflurane
669
VP of sevoflurane
170
BG coefficient of nitrous
0.46
BG coefficient of halothane
2.54
BG coefficient of isoflurane
1.46
BG coefficient of desflurane
0.42
BG coefficient of sevoflurane
0.69
MAC of nitrous oxide
104
MAC of halothane
0.75
MAC of isoflurane
1.2
MAC of desflurane
6
MAC of sevoflurane
2
OG coefficient of nitrous
1.4
OG coefficient of halothane
224
OG coefficient of isoflurane
98
OG coefficient of desflurane
18.7
OG coefficient of sevoflurane
55
What conditions increase MAC?
youth, hyperthermia, hypernatremia, chronic ETOH, stimulants
What conditions decrease MAC?
age, hypothermia, pregnancy, acute ETOH intox, other anesthetics, drugs (benzos, opioids, alpha 2 agonists)
MAC awake
50% respond to verbal stim- 0.2-0.3
MAC bar
block autonomic reflex- 1.7-2x MAC
MAC intubation
2x MAC
ED95
level where 50% don’t respond- 1.3x MAC
Fick’s law of diffusion
rate of diffusion directly proportional to gradient, surface area, and diffusion coefficient, and inversely proportional to membrane thickness
Graham’s law
rate of effusion inversely proportional to square root of molecular weight
Blood gas coefficient
indicates how fast drug gets to site of action
Oil gas coefficient
indicates potency
What does increased CO do to uptake?
uptake increases and induction is slower
What gas is metabolized the most?
halothane
Where is nitrous metabolized?
in the gut by aerobic bacteria
What two gases are structurally similar?
iso and des- differ only by Cl atom
Which gas metabolite is a concern for liver?
halothane- hepatitis
Which gases have the least effect on blunting autoregulation?
isoflurane or desflurane
Who do you avoid using halothane in?
cardiac defects (down’s syndrome)
What gas can cause bradycardia and junctional rhythms at high MAC?
sevo
What gases at higher doses will exhibit sympathetic response?
desflurane and isoflurane
Which gases produce the most “coronary steal”?
iso and des (sevo the least- can use to precondition)
What condition should you avoid the use of nitrous oxide with?
pulmonary hypertension
Describe gas breathing
increased RR, decreased TV
What metabolite is toxic to kidneys?
Compound A from sevo (avoid in renal patients if you can)
How do you reduce production of compound A?
higher flows, keep soda lime fresh, use lower concentration
How do anesthetic gases decrease total hepatic blood flow?
decrease portal vein flow
Complication of N2O use?
reduced immune function- disrupts DNA synthesis by inactivating B12
Contraindication to nitrous?
air containing cavities (air embolus, closed pneumo, etc)
What is the mechanism of malignant hyperthermia?
activation of ryanodine receptors- increased release of calcium from SR–> sustained m. contraction–> increased metabolism= heat production
What are the signs and symptoms of MH?
tachycardia, hypercarbia, hyperthermia, masseter spasm, tachypnea, arrhythmias, metabolic acidosis, m. rigidity, myoglobinemia, hyperkalemia
Treatment for MH
dantrolene, stop agents, 100% O2 with charcoal filter, arterial access, cooling measures
What does dantrolene do and what are the considerations?
blocks coupled calcium entry- causes m. relaxation so may need respiratory support
Which opioid receptor has antishivering effects?
kappa
Order of opioid potency from least to greatest
demerol < morphine < dilaudid < alfentanil < fentanyl < remifentanil < sufentanil
Which opioids have the fastest onset?
fentanyl, sufentanil, remifentanil
Which opioid has the shortest duration of action?
sufentanil (and fentanyl)
What causes cardiovascular effects from opioids?
histamine release (naturally occurring opioids)- venodilation, bradycardia–> hypotension
What can occur with high doses of synthetic opioids?
muscle rigidity- decreased chest wall compliance
What is the longest acting opioid?
morphine
Where is morphine metabolized and what is it conjugated to?
liver- morphine 3 (inactive- seizures), morphine 6 (active- resp depression)
Is morphine more for dull or sharp pain?
dull
Describe codeine
natural occurring opioid, 10% breaks down to morphine, more used for anti-tussive properties than pain
Why would you use Dilaudid over morphine?
renal insufficiency- no active metabolites
Dose of Dilaudid
0.2-0.5 mg IV
What is demerol used for?
post-op shivering
When should you avoid demerol?
renal insufficiency (active metabolite buildup –> seizures), and concurrent use with MAOIs (serotonin syndrome)
Storage site of inactive fentanyl metabolites?
lungs- significant first pass pulmonary uptake
How is remifentanil metabolized?
esterases in blood (majority) and some by N-dealkylation
What can remifentanil boluses cause?
bradycardia unresponsive to vagolytics- may need epi
Rare effect of remifentanil?
hyperalgesia
What opioid is best for chronic pain?
methadone
Why is fentanyl preferred over alfentanil?
longer duration of action
What opioid is preferred for cardiac and airway cases?
sufentanil- significant analgesia
Considerations for using opioids in neuraxial analgesia
smaller doses, watch for respiratory depression, must be preservative free
What is the ceiling effect in regards to agonist-antagonists?
increased doses do not produce additional responses
How do you administer Narcan?
20-40 mcg IV carefully titrated to prevent rapid reversal (can cause sympathetic response, pulmonary edema, severe pain, arrhythmias)
Duration of Narcan?
1-4 hours
When should you avoid using toradol?
renal patients, asthma patients, and ortho (inhibits bone healing)
What stage is a patient at risk for laryngospasm?
stage 2
CV effects of propofol?
tachycardia on induction, decreased SVR, hypotension
Propofol Infusion Syndrome symptoms
acidosis, hypertriglyceridemia, renal failure, bradycardia, hypotension, rhabdo
What are some phenomena that may occur on induction with propofol?
twitching, opisthotonus
What is a common side effect of etomidate?
myoclonus
Does a standard induction dose of etomidate cause apnea?
no
What do you want to ensure before giving barbituates?
adequate volume status (can cause profound vasodilation)
What can barbituates trigger?
acute intermittent porphyria
How is ketamine different from other induction drugs?
sympathomimetic (increased HR, BP, CO), increases ICP, CMRO2; also a NMDA antagonist instead of acting on GABA
What population is ketamine good for?
severe asthmatics
What may ketamine cause?
increased salivation
List benzos in order of shortest to longest half life
versed (2 hours), Ativan (15 hours), valium (30 hours)
Schedule 1 drugs
heroin, LSD, marijuana, qualudes, ecstasy
Schedule 2 drugs
cocaine, meth, pentobarb, fentanyl, codeine
Schedule 3 drugs
barbituates, hydrocodone, ketamine
Schedule 4 drugs
phenobarb, valium, butorphanol
Schedule 5 drugs
buprenorphine, codeine cough syrup
What are the different “tropys”?
ino- force of contraction; chrono- rate; dromo- speed of electrical conduction; lusi- relaxation
How do beta blockers work?
slow phase 4 depolarization
What are the vascular effects of nitric oxide?
vasodilation, antithrombotic, anti-inflammatory, anti-proliferative
What are drugs that act on the nitric oxide pathway?
hydralazine (arterial), nitro (venous), nitroprusside (both)
What is a neuro consequence of using nitro or nitroprusside?
increases ICP
What is a possible complication of nitroprusside?
cyanide toxicity
What are the effects of CCBs?
varying degrees of myocardial depression, vasodilation, activation of ANS
What do ACEIs do?
reduce BP by blocking the conversion of angiotensin I to angiotensin II
What do ARBs do?
reduce BP by blocking angiotensin II receptors
What are some interactions of CCBs with anesthetics?
potentiate m. relaxants and local anesthetics
How do you treat refractory hypotension as a result fo ACEIs?
vasopressin or methylene blue
What are the 4 classes of antidysrythmics?
1- sodium blockers; 2- beta blockers; 3- K blockers; 4- Ca blockers
What is the effect of lidocaine on the heart?
blocks fast Na channels, decreases automaticity, accelerates repolarization
What kind of beta blockers do we prefer to use?
selective- like esmolol
What is amio?
K channel blocker- used for life threatening ventricular rhythms
What kind of CCB is good for neuro cases?
nimodopine (crosses BBB)
